Every site is different, and choosing the right foundation comes down to the ground conditions, the type of build and what works best for the construction programme.
Timber piles are a long-established foundation option for New Zealand residential construction and remain a suitable choice on NZS 3604 good ground. But they aren’t the only option. Engineered screw piles can also be used on good ground, offering a different approach to getting the foundations in.
With the recent changes around granny flats, this is becoming a more relevant option for small residential builds, particularly those using timber floors. You can read more about using Blade Piles for granny flats under the new rules here.
What is “good ground” under NZS 3604?
Good ground is ground that meets the requirements set out in NZS 3604 and is suitable for the standard foundation provisions within the Standard. Where a site meets these requirements, foundations can generally be designed using the relevant NZS 3604 provisions without requiring a fully engineered foundation solution.
Why consider Blade Piles on good ground?
Blade Piles are engineered screw piles designed in accordance with AS 2159:2009. On good ground sites, they can offer:
- Faster installation: Piles are screwed into the ground rather than excavated or driven, making for a quick foundation installation with no concrete curing time.
- Minimal ground disturbance: Installation produces little spoil and no vibration, which can be useful on tight urban sections or around existing buildings and landscaping.
- Flexibility for the future: Blade Piles can be removed and reused if a building is relocated or the foundation layout changes, while also providing flexibility for future extensions or modifications.
Now available for self-install by LBP Builders
For granny flats and other small residential builds with timber floors, we can supply the piles and provide the technical requirements, while a Licensed Building Practitioner (LBP) handles the installation as part of their own build. This means no waiting for a piling crew and gives builders more control over their own construction programme.
Find out more about self-installing Blade Piles
When is a fully engineered Blade Pile design the right call?
Sites with ground conditions outside the scope of NZS 3604,such as uncontrolled fill, peat, soft or compressible soils, liquefaction-prone ground, high groundwater or expansive clay, require specific engineering. Blade Piles are also used where the site or building creates other foundation challenges, including house extensions, bridging services around existing infrastructure, seismic retrofit work, and sites where excavation needs to be minimised due to contamination or archaeological constraints.
A geotechnical assessment establishes the site’s ground conditions and bearing capacity. From there, an engineer completes the pile design, including pile depth and layout, to suit your site.
More than 150 engineering firms across New Zealand have experience designing Blade Piles. If your site falls outside the scope of NZS 3604, we can help connect you with a local firm to undertake the required foundation work.